Conventional planar printed wiring boards (PWBs) have been replaced by three-dimensional molded circuit boards in many applications, such as in cellular telephones, pagers and computers. The three-dimensional circuit boards act as a substrate for the metallized circuitry, plated through-holes and electronic components which are subsequently mounted onto the circuitry.
These molded circuit boards are normally comprised of polymeric materials such as polyetherimide (PEI), acrylonitrile-butadiene-styrene (ABS) and polypropylene (PP), which have large coefficients of thermal expansion (CTE) relative to the metallization and the electronic components. This difference in CTE can degrade the long term reliability of the final electronic assembly when exposed to repetitive thermal variations. The molded circuit board is also susceptible to electromagnetic interference (EMI) which affects the function of the circuitry.